1 Ganglia-groups of neuron cell bodies that lie peripheral to the central nervous system in vertebrates. 2  Bipolar neurons-cell body located near the middle of the axon; characteristic of retinal neurons. 3  Unipolar neurons-cell body lies off to one side of axon; characteristic of sensory neurons.
The principal host for diamonds are rocks formed in the earth's mantle that are known as eclogite and peridotite that are carried to the earth's surface in magmas known as kimberlit e and lamproite.
Experiments and the high density of diamonds tell us that they crystallize at very high pressures. In nature this means that diamonds are created by geologic processes at great depth within Earth, generally more than 150 kilometers down, in a region beneath the crust known as the mantle. Other processes, explored later in this exhibition, bring diamonds to where people can find them. This diagram shows the interior structure of Earth. The three concentric layers -- the core, mantle, and crust -- formed within a few hundred million years of Earth's coalescence 4.5 billion years ago. The core is primarily an iron-nickel alloy and makes up a large fraction of the mass of Earth.